/*
 * Copyright 2002-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.messaging.simp.user;

import java.util.Set;

import org.springframework.lang.Nullable;

/**
 * A registry of currently connected users.
 *
 * @author Rossen Stoyanchev
 * @since 4.2
 */
public interface SimpUserRegistry {

    /**
     * Get the user for the given name.
     *
     * @param userName the name of the user to look up
     * @return the user, or {@code null} if not connected
     */
    @Nullable
    SimpUser getUser(String userName);

    /**
     * Return a snapshot of all connected users.
     * <p>The returned set is a copy and will not reflect further changes.
     *
     * @return the connected users, or an empty set if none
     */
    Set<SimpUser> getUsers();

    /**
     * Return the count of all connected users.
     *
     * @return the number of connected users
     * @since 4.3.5
     */
    int getUserCount();

    /**
     * Find subscriptions with the given matcher.
     *
     * @param matcher the matcher to use
     * @return a set of matching subscriptions, or an empty set if none
     */
    Set<SimpSubscription> findSubscriptions(SimpSubscriptionMatcher matcher);

}
